The present invention relates to expansion tanks or accumulators of the type in which a flexible diaphragm is positioned across the interior of the tank to separate it into two or more compartments or chambers to be occupied by pressurized fluids. Generally one of the fluids is air and the other a liquid such as water or a hydraulic liquid such as a brake fluid.
Expansion tanks or accumulators of the type to which the present invention is directed are commonly incorporated in a system where fluctuations in pressure are normally anticipated. The expansion tank, as the name implies, serves to introduce an element of resiliency into the hydraulic circuit so as to be able to absorb the surges of pressure which can be expected to occur. At such times the increased hydraulic pressure is transmitted to the liquid within the liquid chamber of the tank, the volume of such chamber increasing and, by virture of the diaphragm, compressing the air within the other chamber of the tank to effectively cushion the surge of pressure. The consequence is that the hydraulic system is safeguarded against sudden increases in hydraulic pressure which might otherwise cause substantial damage to the system or to sensitive components therein.
It has been conventional to construct the expansion tank of a pair of shell halves each of which may be hemispheric in configuration terminating in generally radially extending skirts or flanges. The peripheral edge of the diaphragm is given a configuration providing a protuberance in the form of a thickened bead that is complementary to a recessed portion formed in one or both of the shell skirts or flanges. The peripheral edge of the diaphragm is thus securable between the skirts of the shells to seal the joint therebetween. Frequently the joint so formed is maintained by means of a clamping ring adapted to apply a closing force to the mating skirt or flange sections of the shells. Such a construction is disclosed, for example, in U.S. Pat. No. 2,394,401 issued Feb. 5, 1946 to J. W. Overbeke. Typical also of conventional expansion tank construction is the device disclosed in U.S. Pat. No. 2,300,722 issued Nov. 3, 1942 to H. W. Adams et al. In the Adams patent the peripheries of the shell halves are shown as being drawn together by means of a series of circumferentially spaced bolts and nuts. The diaphragm, in structures such as those of Overbeke and Adams et al, thus serves to seal the joint between the shell halves of the tank and be anchored in one or both of the skirts or flanges.
Certain disadvantages are inherent in expansion tanks of the type shown in the Overbeke and Adams et al. patents and in the diaphragms utilized. One such disadvantage is the requirement that the peripheral flanges of the tank shell halves undergo special forming operations in order to provide the selected recess configuration for reception of the mating peripheral edge portion of the diaphragm. This, of course, results in increased manufacturing costs. Another disadvantage arises through extended use of the tank and diaphragm. It has been found that due to repeated flexure of the diaphragm under the influence of the pressures exerted in both chambers of the tank the bead or other protuberance of the peripheral edge of the diaphragm tends to become distorted resulting in a loose seating within the recess. This leads to a less than intended optimum sealing of the joint between the flanges of the shell halves and consequent leakage of fluid from the tank. Additionally, during periods when the diaphragm is stressed by a pressure surge the portion of its peripheral edge designed to serve as a sealing element frequently tends to be temporarily unseated thereby establishing communication between one or both of the pressurized chambers of the tank and the ambient environment so as to reduce the effectiveness of the seal.
In view of the foregoing it is one object of this invention to provide an improved diaphragm for an expansion tank for pressurized fluids which is capable of enhanced sealing of the joint between the shell halves of the tank.
It is another object of the invention to provide an expansion tank for pressurized fluids comprising a pair of shell halves that are sealable relative to each other by the peripheral edge of a diaphragm therewithin which shell halves include peripheral flanges of simplified construction.
It is still another object of this invention to provide an expansion tank of the character described which is capable of being stored and/or transported in an arrangement utilizing a minimum of space.
Other objects and advantages of the invention will become readily apparent to persons versed in the art to which the invention pertains from the ensuring description.